<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>04_JS流程控制</title>
</head>
<body>
<script>
    //1.顺序结构
    console.log('1');
    console.log('2');
    console.log('3');

    //2.分支结构
    let uname="";
    if(!uname){
        alert('请先登录!');
    }else{
        alert('欢迎您'+uname);
    }
    ///3.选择分支
    let gender = 100;
    switch (gender) {
        case 1:
            console.log('男');
            break;
        case 0:
            console.log('女');
            break;
        default:
            console.log('未知');
    }

    //4.循环结构
    let names = ['张三','李四','王五'];
    for (var i = 0; i < names.length; i++) {
        console.log(names[i]);
    }
    console.log('循环结束');
    //如果用var定义循环变量i,循环结束后会在此处仍然打印出i的值
    //但用let定义循环变量i,就会报错：ReferenceError: i is not defined
    console.log(i);


    //5.增强for循环
    //n就是names数组中的每次被遍历到的元素
    for (let n of names) {
        console.log(n);
    }









</script>
</body>
</html>